Girlfriend:
My girlfriend is a sexy 19 year old (I am 21) who I met last year when we both started university. She is a lingerie model in her spare time, but she is still quite nervous with showing skin (wants light turned off in bed and won't let me see her breasts) due to her being raped twice by her best male friend some years ago. She is smart and we both share several of the same hobbies, we started swimming several times a week together, and we attend most parties or other events together.


Situation:
We have been together for 8 month officially and dated 2 month more. I got my own apartment and we are talking about her moving in this summer. We have previous had some problems with guys stalking her (see my other thread) but I got taken care of this.

The only quite problem we have had was that she talked with her ex. Back then I dealt with it by talking with my exes and some of the girls I had dated up to I met my girlfriend. Eventually we talked out and she said she would stop talking with her ex boyfriend(they were together 3 years) and I stopped talking to mine.


1st Problem:

This weekend she spend at my place, while I studied she did some stuff on my ipad. I didn't realize it before this Monday when a message pop up, on my Ipad, that she had a new message on fb. I clicked there to enter facebook and logout when I was redirected to my girlfriends conversation with her ex. I got a bit confused when I saw that she wrote back to him and they were talking about seeing each other. I regret it now, but I read more of their conversation. It shows that my girlfriend and her ex had been talking about meeting for quite some time. From what I could read they didn't meet because her ex got a bit annoyed over my girlfriend canceling their meetings.

2nd Problem:

This weekend we both went to a housewarming at one of ours common friend. Our common friend asked us to try to talk to different people so the party wouldn't end with each group sitting for themselves. We did that, I talked with some girls and boys and my girlfriend talked with boys. I noticed in my girlfriends behavior that she were quite flirting. Like leaning up against the guy, having her arm on his shoulder when they sat and so on. When we got home she told me the guy had asked her if she would join him running. I saw her messages on facebook with him and he are really flirting and writing stuff like she is such a beautiful girl and if she think its okay with her boyfriend if they go running together, and it's a shame she got a boyfriend.

My Efforts:

Haven't really done so much, I told her that of course could she go running with the guy (I don't wanna come of as to insecure). I am deeply in love with her, and are afraid that love is blinding me from seeing this situation clear. The reason for asking for advices here, with what there might only be one solution, is that I deeply down want this relationship to work, and my school friends are either to AFC and will advice me to stay and work with our relationship, while my party and army buddy's will advice me to get out and get laid (after i dumb her).

I would like some advice from you fellow gamers on how to tackle this situation, any advices or comments will be appreciated

Well, I won't lie, its a shitty situation. Your gf is definitely not treating you right.
Her talking to the ex behind your back is a red flag. The fact that she cancels on meeting with him is good, and means she has second thoughts, but its on her mind, and that's a big problem.
Flirting at the party in front of you is a shit test. She's looking for your reaction. If she's being blatant in her flirting with other guys, you need to set your foot down and tell her she needs to cut that shit out (at the right place and time, don't start drama at the party). She will instantly start drama and start accusing you of being paranoid, insecure, etc etc etc. Don't get involved in that shitstorm any further. Ignore it. Tell her if it continues behaving that way the relationship is over, and hold yourself to that commitment. Some would say let her catch you flirting with others, but that would honestly come off as the wrong reaction, especially if you're not really smooth and successful at it, and the girls you're talking to are not comparable to her as far as looks go. If you want to do it right, flirt with others BEHIND her back, and the success will give you the attitude you need to handle this girl.
I wouldn't worry too much about the running guy. He's clearly a tool and based on the shit he says, he's just unintentionally making himself a friendzone candidate in her mind.
If you really did find out about the ex unintentionally (instead of going stalkermode), and you have a believable story of how you found out, you have the option of the following gamble. Tell her what you saw (with the ex only, don't mention the running tool), how you saw, and tell her you two are done. And leave. It's a very valid reason for a breakup and what she did was unacceptable, and by breaking up with her because of such behavior you are demonstrating higher value, by not being willing to put up with it.
The gamble is in that she might not come back, but if she does, make your position as the man clear. Tell her you will not get back together unless the exes are gone, the flirting stops, and she treats you with respect. it should fix your problems for a while. If she does not, you have to avoid ever contacting her again under any circumstances, and move on from your losses. The consolation is, if she doesn't come back, the relationship was already doomed, and the chance that you could have saved any other way was very slim.
Good luck mate.

Drop her like a stripper drops her ass to the ground... quick.

Well, to make this case more interesting, I had a talk with my girlfriend over the phone.
She told me she have had a boring day, then she told me all what the guy from the weekend had wrote to her on facebook, and she told me she were like "wtf is this guy thinking?" and then she told me she teased him by writing "oh I wanna do so many nasty things..." followed by "with my boyfriend".

She asked me why I had been so quite the last few days. I tried to change subject but she kept asking, and asked if she had done anything. She even asked "now you don't dump tomorrow when I come visiting you?". Eventually, I told her, that the reason why I had been a bit quiet was because of her and the boy. I told her that I didn't have any problem at all with her flirting, that I even enjoyed seeing boys try hard with her, but that she had caught me off guard when she told me she had en running "date" with the guy. Then she went bla bla bla and that I should just pull her aside if I were unhappy with the way she behaved when we were out.

I think I handle this decently. It could easily have went worse, but again, if I was a bit prepared I might have done this conversation a lot better.

I still see a red flag with her not telling me about her ex. I'm not quite sure if I should just man the fuck up and tell her that I don't wanna be with some young girl who are writing with her ex and even trying to be more "valuable" in her ex bf eyes.
Or I could act as I didn't knew anything and then man up big time the next time she do something like this.

Also, I could just dump her even though I gonna eat 1 big box of icecream before starting to date again.

What do you guys think? Could any of this work, or am I still blinded by love?

You made a ton of really awful mistakes during that phone call I'm afraid. At this point I doubt you can bring up the ex and facebook without being called on a bluff. You should mellow out a bit and reduce the drama if you still want this to work. But honestly, I don't know what to suggest at this point. See if she acts better, if not, then soft next, if she's still not responding, hard next.

Personally I'd drop this girl, the talking to the ex and trying to meet up with him behind your back is not acceptable behavior. The fact that she hasn't brought up this leads me to believe that she's doing other things that you wouldn't approve of.

- Just talk to her and tell her straight what you don’t like about her. It is up to her if she will continue what she started. But if she did, it is up to you if you want to fight for your relationship or not.

Drop like a moldy hot potato